This invention relates to axial piston fluid devices, and more particularly to means for lubricating bearings in such fluid devices.
Axial piston pumps and motors routinely include a rotating cylinder barrel connected to a shaft and containing a plurality of pistons whose ends work against an inclined surface to draw fluid into the cylinders as the pistons are extended and to force fluid out of the same cylinders as the pistons are retracted. The cylinder barrels are commonly journaled in the inner diameter of a large barrel bearing which is mounted in the cavity of the pump or motor housing. Presently, such barrel bearings are typically sleeve bearings with an anti-friction coating on their inner diameter. The shaft which mounts the cylinder barrel is typically supported in a ball bearing at one end of the housing and in a sleeve bearing or bushing at the other end of the housing.
Leakage from the rotating group will result in fluid accumulating in the cavity of the housing. This fluid is typically used to lubricate the moving parts, including the bearings such as the barrel bearing. However, unless there is a pressure differential across the width of the bearings or bushings, there is no assurance that the engaging rotating surfaces will in fact be lubricated.
In our invention we provide a positive means for lubricating the shaft bushing and means for assuring lubrication of the mating surfaces of the barrel bearing and the cylinder barrel even if there is no pressure differential axially across the width of the barrel bearing.